/***
 * Copyright 2002-2010 jamod development team
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 ***/

package net.wimpi.modbus.io;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutput;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.IOException;
import java.net.Socket;
import java.net.SocketException;

import net.wimpi.modbus.Modbus;
import net.wimpi.modbus.ModbusIOException;
import net.wimpi.modbus.msg.ModbusMessage;
import net.wimpi.modbus.msg.ModbusRequest;
import net.wimpi.modbus.msg.ModbusResponse;
import net.wimpi.modbus.util.ModbusUtil;

/**
 * Class that implements the Modbus transport flavor.
 *
 * @author Dieter Wimberger
 * @version @version@ (@date@)
 */
public class ModbusTCPTransport implements ModbusTransport
{

    // instance attributes
    private DataInputStream m_Input; // input stream
    private DataOutputStream m_Output; // output stream
    private BytesInputStream m_ByteIn;

    /**
     * Constructs a new <tt>ModbusTransport</tt> instance, for a given
     * <tt>Socket</tt>.
     * <p>
     * 
     * @param socket
     *            the <tt>Socket</tt> used for message transport.
     */
    public ModbusTCPTransport(Socket socket)
    {
        try
        {
            setSocket(socket);
        }
        catch (IOException ex)
        {
            if (Modbus.debug)
                System.out.println("ModbusTCPTransport::Socket invalid.");
            // @commentstart@
            throw new IllegalStateException("Socket invalid.");
            // @commentend@
        }
    }// constructor

    /**
     * Sets the <tt>Socket</tt> used for message transport and prepares the
     * streams used for the actual I/O.
     *
     * @param socket
     *            the <tt>Socket</tt> used for message transport.
     * @throws IOException
     *             if an I/O related error occurs.
     */
    public void setSocket(Socket socket) throws IOException
    {
        prepareStreams(socket);
    }// setSocket

    public void close() throws IOException
    {
        m_Input.close();
        m_Output.close();
    }// close

    public void writeMessage(ModbusMessage msg) throws ModbusIOException
    {
        try
        {
            msg.writeTo((DataOutput) m_Output);
            m_Output.flush();
            // write more sophisticated exception handling
        }
        catch (Exception ex)
        {
            throw new ModbusIOException("I/O exception - failed to write.");
        }
    }// write

    public ModbusRequest readRequest() throws ModbusIOException
    {

        // System.out.println("readRequest()");
        try
        {

            ModbusRequest req = null;
            synchronized (m_ByteIn)
            {
                // use same buffer
                byte[] buffer = m_ByteIn.getBuffer();

                // read to byte length of message
                if (m_Input.read(buffer, 0, 6) == -1)
                {
                    throw new EOFException(
                            "Premature end of stream (Header truncated).");
                }
                // extract length of bytes following in message
                int bf = ModbusUtil.registerToShort(buffer, 4);
                // read rest
                if (m_Input.read(buffer, 6, bf) == -1)
                {
                    throw new ModbusIOException(
                            "Premature end of stream (Message truncated).");
                }
                m_ByteIn.reset(buffer, (6 + bf));
                m_ByteIn.skip(7);
                int functionCode = m_ByteIn.readUnsignedByte();
                m_ByteIn.reset();
                req = ModbusRequest.createModbusRequest(functionCode);
                req.readFrom(m_ByteIn);
            }
            return req;
            /*
             * int transactionID = m_Input.readUnsignedShort(); int protocolID =
             * m_Input.readUnsignedShort(); int dataLength =
             * m_Input.readUnsignedShort(); if (protocolID !=
             * Modbus.DEFAULT_PROTOCOL_ID || dataLength > 256) { throw new
             * ModbusIOException(); } int unitID = m_Input.readUnsignedByte();
             * int functionCode = m_Input.readUnsignedByte(); ModbusRequest
             * request = ModbusRequest.createModbusRequest(functionCode,
             * m_Input, false); if (request instanceof IllegalFunctionRequest) {
             * //skip rest of bytes for (int i = 0; i < dataLength - 2; i++) {
             * m_Input.readByte(); } } //set read parameters
             * request.setTransactionID(transactionID);
             * request.setProtocolID(protocolID); request.setUnitID(unitID);
             * return request;
             * 
             */
        }
        catch (EOFException eoex)
        {
            throw new ModbusIOException(true);
        }
        catch (SocketException sockex)
        {
            // connection reset by peer, also EOF
            throw new ModbusIOException(true);
        }
        catch (Exception ex)
        {
            ex.printStackTrace();
            throw new ModbusIOException("I/O exception - failed to read.");
        }
    }// readRequest

    public ModbusResponse readResponse() throws ModbusIOException
    {
        // System.out.println("readResponse()");

        try
        {

            ModbusResponse res = null;
            synchronized (m_ByteIn)
            {
                // use same buffer
                byte[] buffer = m_ByteIn.getBuffer();

                // read to byte length of message
                if (m_Input.read(buffer, 0, 6) == -1)
                {
                    throw new ModbusIOException(
                            "Premature end of stream (Header truncated).");
                }
                // extract length of bytes following in message
                int bf = ModbusUtil.registerToShort(buffer, 4);
                // HOTFIX 1.0.3: extract the transaction id
                int transactionId = ModbusUtil.registerToShort(buffer, 0);
                // read rest
                if (m_Input.read(buffer, 6, bf) == -1)
                {
                    throw new ModbusIOException(
                            "Premature end of stream (Message truncated).");
                }
                m_ByteIn.reset(buffer, (6 + bf));
                m_ByteIn.skip(7);
                int functionCode = m_ByteIn.readUnsignedByte();
                m_ByteIn.reset();
                res = ModbusResponse.createModbusResponse(functionCode);
                res.setTransactionID(transactionId);
                res.readFrom(m_ByteIn);
            }
            return res;
            /*
             * try { int transactionID = m_Input.readUnsignedShort();
             * //System.out.println("Read tid="+transactionID); int protocolID =
             * m_Input.readUnsignedShort();
             * //System.out.println("Read pid="+protocolID); int dataLength =
             * m_Input.readUnsignedShort();
             * //System.out.println("Read length="+dataLength); int unitID =
             * m_Input.readUnsignedByte();
             * //System.out.println("Read uid="+unitID); int functionCode =
             * m_Input.readUnsignedByte();
             * //System.out.println("Read fc="+functionCode); ModbusResponse
             * response = ModbusResponse.createModbusResponse(functionCode,
             * m_Input, false); if (response instanceof ExceptionResponse) {
             * //skip rest of bytes for (int i = 0; i < dataLength - 2; i++) {
             * m_Input.readByte(); } } //set read parameters
             * response.setTransactionID(transactionID);
             * response.setProtocolID(protocolID); response.setUnitID(unitID);
             * return response;
             */
        }
        catch (Exception ex)
        {
            // ex.printStackTrace();
            throw new ModbusIOException("I/O exception - failed to read.");
        }
    }// readResponse

    /**
     * Prepares the input and output streams of this <tt>ModbusTCPTransport</tt>
     * instance based on the given socket.
     *
     * @param socket
     *            the socket used for communications.
     * @throws IOException
     *             if an I/O related error occurs.
     */
    private void prepareStreams(Socket socket) throws IOException
    {

        m_Input = new DataInputStream(
                new BufferedInputStream(socket.getInputStream()));
        m_Output = new DataOutputStream(
                new BufferedOutputStream(socket.getOutputStream()));
        m_ByteIn = new BytesInputStream(Modbus.MAX_IP_MESSAGE_LENGTH);
    }// prepareStreams

}// class ModbusTCPTransport
